177,603 research outputs found
Documents sur les précurseurs. Deux instituteurs kabyles : A. S. Boulifa et M. S. Lechani
No full textChaker Salem. Documents sur les précurseurs. Deux instituteurs kabyles : A. S. Boulifa et M. S. Lechani. In: Revue de l'Occident musulman et de la Méditerranée, n°44, 1987. Berbères, une identité en construction. pp. 97-115
Invited Article: ultra-broadband terahertz coherent detection via a silicon nitride-based deep sub-wavelength metallic slit
No full textWe present a novel class of CMOS-compatible devices aimed to perform the solid-state-biased coherent detection of ultrashort terahertz pulses, i.e., featuring a gap-free bandwidth at least two decades-wide. Such a structure relies on a 1-mu m-wide slit aperture located between two parallel aluminum pads, embedded in a 1-mu m-thick layer of silicon nitride, and deposited on a quartz substrate. We show that this device can detect ultra-broadband terahertz pulses by employing unprecedented low optical probe energies of only a few tens of nanojoules. This is due to the more than one order of magnitude higher nonlinear coefficient of silicon nitride with respect to silica, the nonlinear material employed in the previous generations. In addition, due to the reduced distance between the aluminum pads, very high static electric fields can be generated within the slit by applying extremely low external bias voltages (in the order of few tens of volts), which strongly enhance the dynamic range of the detected THz waveforms. These results pave the way to the integration of solid-state ultra-broadband detection in compact and miniaturized terahertz systems fed by high repetition-rate laser oscillators and low-noise, low-voltage generators
CFD simulation of water injection in GT inlet duct using spray experimentally tuned data: Nozzle spray simulation model and results for an application to a heavy-duty gas turbine
No full textThis study describes an application of Computational Flow Dynamics (CFD) to the two-phase flow problem of water injection into a compressor inlet duct for fogging systems. The paper addresses issues related to the CFD setup and the developed spray simulation model. Water injection is simulated by fitting experimental data on sprays obtained from industrial nozzles. In particular, the initial droplets size distribution is defined in accordance with results of laboratory tests on impaction-pin type nozzles. By using a commercial CFD software, 3D numerical simulations have been carried out on a typical gas turbine inlet duct. The effects of the duct geometry, filter and silencer on the duct internal air flow-field were analyzed. Finally, the effect of water injection carried out by means of an array of nozzles in the inlet duct is investigated. The paper presents the CFD twophase results obtained for the application case under study; the analysis of the compressor bellmouth conditions due to the evaporation phenomenon is included in the paper. Copyright © 2007 by ASME
Simulation of thermal plant optimization and hydraulic aspects of thermal distribution loops for large campuses
No full textFollowing an introduction, the author describes Texas A&M University and its utilities system. After that, the author presents how to construct simulation models for chilled water and heating hot water distribution systems. The simulation model was used in a $2.3 million Ross Street chilled water pipe replacement project at Texas A&M University. A second project conducted at the University of Texas at San Antonio was used as an example to demonstrate how to identify and design an optimal distribution system by using a simulation model. The author found that the minor losses of these closed loop thermal distribution systems are significantly higher than potable water distribution systems. In the second part of the report, the author presents the latest development of software called the Plant Optimization Program, which can simulate cogeneration plant operation, estimate its operation cost and provide optimized operation suggestions. The author also developed detailed simulation models for a gas turbine and heat recovery steam generator and identified significant potential savings. Finally, the author also used a steam turbine as an example to present a multi-regression method on constructing simulation models by using basic statistics and optimization algorithms. This report presents a survey of the author??s working experience at the Energy Systems Laboratory (ESL) at Texas A&M University during the period of January 2002 through March 2004. The purpose of the above work was to allow the author to become familiar with the practice of engineering. The result is that the author knows how to complete a project from start to finish and understands how both technical and nontechnical aspects of a project need to be considered in order to ensure a quality deliverable and bring a project to successful completion. This report concludes that the objectives of the internship were successfully accomplished and that the requirements for the degree of Degree of Engineering have been satisfied
Intern experience at CH���M Hill, Inc.: an internship report
No full textIncludes author's vita"Submitted to the College of Engineering of Texas A&M University in partial
fulfillment of the requirement for the degree of Doctor of Engineering."Includes bibliographical referencesA review of the author's internship experience with CH���M HILL, Inc.
during the period September 1975 through May 1976 is presented. During this nine month
internship the author worked as an Engineer II in the Industrial Processes discipline of this
large consulting engineering firm... The author's prime responsibility was as one of three
lead design engineers on the design of a large wastewater treatment facility for a pulp mill
in Hoquiam, Washington owned by ITT Rayonier Inc. The work generally consisted of the design
of individual treatment units and associated piping and pumping. The purpose of the project
was to provide wastewater treatment capabilities that would satisfy the effluent limitations
(standards) imposed upon the mill by the State of Washington Department of Ecology and the
U.S. Environmental Protection Agency. The author's assignment also entailed necessary
interaction with the project manager and other CH���M HILL design engineers and support staff
members, the client's representatives, and representatives of two other consulting engineering
firms working on the project. Thus, the internship position at CH���M HILL provided considerable
experience coordinating the author's work with the work of other engineers, guiding the design
and administrative efforts of a support staff, and interacting regularly with the client and
other consulting firms. This broad exposure to a variety of engineering and organizational
problems provided a valuable educational experience
Intern experience at the Texas Transportation Institute: an internship report
No full text"Submitted to the College of Engineering of Texas A&M University in partial
fulfillment of the requirements for the degree of Doctor of Engineering."Includes vita (leaf 91)Includes bibliographical references (leaf 57)This report discusses the author's engineering experience at the Texas
Transportation Institute (TTI), Texas A&M University from March 1974 through July 1977. A
report of this experience plus twelve additional hours of academic course work were
substituted for an internship according to requirements established by the College of
Engineering. Although the author could not retroactively establish objectives of the type
associated with a typical internship, the work experience gained could be related to the two
general objectives of an intership: 1. To demonstrate an identifiable contribution to the
organization in which the intern served, and 2. To enable the intern to become aware of the
non-technical aspects of working as an engineer in a non-academic environment. While a member
of the Texas Transportation Institute staff, the author worked on a number of projects in the
areas of highway traffic engineering research and the preparation of continuing education
courses for transportation engineering officials. These assignments were contained within the
Urban Transportation Systems Division of TTI. This report delineates the author's contribution
to four particular projects and discusses the technical as well as non-technical experience
gained from each. Having been exposed to more engineering situations than many of the other
Doctor of Engineering students, the author has already formulated some rather specific
milestones for the future. The Doctor of Engineering program is discussed in conjunction with
its potential for helping the author attain these career goals and objectives. Also, some
thoughts are presented regarding the Doctor of Engineering as a viable alternative to the
Ph.D. in preparing for a career in engineering higher education
Regularity estimates for fractional orthotropic p-Laplacians of mixed order
No full textChaker J, Ki M. Regularity estimates for fractional orthotropic p-Laplacians of mixed order. Advances in Nonlinear Analysis . 2022;11(1):1307-1331.We study robust regularity estimates for a class of nonlinear integro-differential operators with anisotropic and singular kernels. In this paper, we prove a Sobolev-type inequality, a weak Harnack inequality, and a local Holder estimate
Experience on biocompatible artificial hair implant
No full textOBJECTIVE: In Europe, a great number of investigations and studies followed up to develop safer techniques performed by physicians only. Successful dedicated medical protocols included the implant of single fibers with extractable root. The aim of our study was to evaluate the efficacy of biocompatible artificial hair implants in patients with androgenetic alopecia.PATIENTS AND METHODS: 682 patients (488 males and 184 females) aged between 25 and 70 years old, with diagnosed AGA, requiring no invasive nor surgical hair restoration, with problems of baldness and refusing surgical options appealed to the Second Opinion Medical Consulting (Modena, Italy), and were included in the present protocol. Before the treatment, all patients underwent a test implant to rule out hypersensitivity by implanting 100 fibers on a selected skin spot. If no reaction was detected, five weeks later 5001,200 fibers were further implanted per session at a minimum interval of 5 weeks until the required aesthetic result was achieved.RESULTS: The average number of sessions for each patient was 5. The average number of implanted fibers was 2,100 (ranging from 800 to 12,000). The treated scalp area returned to normal appearance and tenderness in 3 days.CONCLUSIONS: The socio-phycological benefit and the life quality improvement of our patients have been the focus of the study. On our side, the accurate selection, small hair units for each implant session, customized dermatological consultation and the use of highly biocompatible fibers have been the proper strategy to achieve the goal
The long-wavelength view of GG Tau A: rocks in the ring world
No full textWe present the first detection of GG Tau A at centimetre wavelengths, made with the Arcminute Microkelvin Imager Large Array at a frequency of 16 GHz (λ = 1.8 cm). The source is detected at >6 σrms with an integrated flux density of S16GHz = 249 ± 45 µJy. We use these new centimetre-wave data, in conjunction with additional measurements compiled from the literature, to investigate the long-wavelength tail of the dust emission from this unusual protoplanetary system. We use an MCMC-based method to determine maximum likelihood parameters for a simple parametric spectral model and consider the opacity and mass of the dust contributing to the microwave emission. We derive a dust mass of Md ~ 0.1 Msun, constrain the dimensions of the emitting region and find that the opacity index at λ > 7 mm is less than unity, implying a contribution to the dust population from grains exceeding ~4 cm in size. We suggest that this indicates coagulation within the GG Tau A system has proceeded to the point where dust grains have grown to the size of small rocks with dimensions of a few centimetres. Considering the relatively young age of the GG Tau association in combination with the low derived disc mass, we suggest that this system may provide a useful test case for rapid core accretion planet formation models
Harnack inequality for nonlocal problems with non-standard growth
No full textChaker J, Ki M, Weidner M. Harnack inequality for nonlocal problems with non-standard growth. Mathematische Annalen . 2022;386:533–550 .We prove a full Harnack inequality for local minimizers, as well as weak solutions to nonlocal problems with non-standard growth. The main auxiliary results are local boundedness and a weak Harnack inequality for functions in a corresponding De Giorgi class. This paper builds upon a recent work on regularity estimates for such nonlocal problems by the same authors
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